This invention concerns an injector pack.
It is common for sufferers from arthritis to give themselves injections, but often they have difficulty, by virtue of their condition, in handling and using syringes.
It is the aim of this invention to provide a pack containing an injection device stored in a safe and disassembled condition, but which can easily be assembled, cocked and fired, even by those with impaired manual dexterity.
According to the present invention there is provided an injector pack comprising a box, a syringe housing, and a firing mechanism attachable to the housing and having an actuator to release a plunger from a retracted position to propel a syringe within the housing to project its needle from the housing and then to express a dose through the needle, wherein the box has internal structure which constrains the actuator into a safe condition when the firing mechanism is in a stowed position therein, and which stows the syringe housing separately to present its rear end for the attachment of the firing mechanism when that is removed from its stowed position, the syringe housing being removable from the box by the attached firing mechanism and the actuator being adjustable when the firing mechanism is free of the box to a cocked condition where it can be manipulated to release the plunger.
Conveniently, with the plunger retracted, the actuator will be rotatable between the safe condition and the cocked condition. This rotation may also be carried out with the plunger released or fired.
In the preferred form, the firing mechanism has a barrel from the forward end of which the plunger emerges, and the actuator is tubular, sleeved over the barrel (so that it can serve as a grip), and with a closed rear end which forms part of the plunger release. The barrel can have a seat in a lower part of the box and the actuator a seat in the box above the barrel seat. These seats can be non-circular and in a relationship to ensure that the relative rotational positions of the barrel and actuator put the actuator in the safe condition.
The actuator seat may be a regular, substantially polygonal socket to receive a complementary formation on the actuator symmetrical about the axis of the barrel. The barrel seat may include an annular array of cams for engagement by a complementary array of cams around the barrel at its leading end. The engagement of the cams then causes or confirms rotation of the barrel to a position where the actuator is in the safe condition.
Conveniently, the plunger is tubular, at least at its leading end. A pin upstanding within the box can then enter the plunger and guide it, and thus the firing mechanism, as that mechanism is stowed in the box.
It is desirable for the actuator to be in its safe condition before the plunger can be held in its retracted position. In other words, if the mechanism has been fired, it cannot be re-cocked simply by pressing back the plunger; there also has to be mutual rotation between the actuator and the barrel.
The box can have an internal pillar, separate from the stowed positions of the syringe housing and the firing mechanism for assisting retraction of the plunger, the tip of the pillar being engageable by the leading end of the plunger when that is offered up in alignment, while the leading portion of the firing mechanism can be telescoped down over the pillar, the plunger thereby being pushed backwards.
Additionally, the pillar may have an annular array of cams around its base similar to those of the barrel seat, and the box may have an actuator guide in registry with the pillar. This can ensure that, as the barrel is sleeved over the pillar and the plunger reaches its fully retracted position, the relative rotational positions of the barrel and the actuator are such that the actuator is in its safe condition.
Preferably the syringe housing will be held against rotation when stowed in the box. If the firing mechanism screw couples to the housing, as is preferred, holding the box holds the housing fast while the firing mechanism is rotated. This turning of the firing mechanism to tighten the screw coupling should be in the same direction as rotating the actuator from the cocked to the safe condition.
The leading end of the syringe housing will preferably have a needle cover, lightly sprung, normally to project beyond the housing and shroud the needle after use. The needle itself will generally have a rubber cap for further protection and hygiene, and in the lower part of the box that locates the housing there can be a formation of known type to strip off the cap when the housing is removed.
Preferably, there will be a window in the grip, and a mark or sign on the barrel which will register with this window when the firing mechanism is safe. Another mark or sign may show when it is cocked.